The invention relates to a device for coating substrates by means of high-velocity flame spraying.
Devices of this kind as discussed are known in a wealth of different embodiments and are employed for a wide variety of different purposes. For instance, they are employed to surface coat a great variety of substrates to render them resistant to temperature and/or wear and/or attrition and/or chemical attack.
Known from prior art are devices fueled by gas and also devices fueled by a liquid fuel, generic devices usually featuring at least one connection for the fuel and another connection for an oxidative gas. It is especially devices that are fueled liquid that may feature a further connection for compressed air. However, all of these known devices suffer from the drawback that their scope of application is limited.
Described in German patent DE 44 29 142 A1 is a head for high-velocity flame spraying powderized materials. This flame spraying head can be simultaneously fueled with two fuels (diesel/fuel oil and a fuel gas), the main fuel being diesel or fuel oil having a carbonizing content exceeding 0.5% by weight. To achieve as clean a combustion of the main fuel as possible permitting preevaporation of the fuel-oil and thus non-carbonizing combustion an evaporating flame is generated upstream of the actual main flame in the direction of flow of the gases. Thus, to achieve clean combustion of the main fuel free of residue both fuels always need to be fed simultaneously.
European patent EP 0 458 018 A2 discloses a HVOF burner comprising a primary combustion chamber and a secondary combustion chamber, both of which are fueled with separate fuels. The primary combustion chamber serves to melt the spray material which is then supersonically accelerated in the subsequent secondary combustion chamber so that it is gunned ultimately from the burner with high kinetic energy. Thus this burner too, always requires both gases to be fueled simultaneously.
In conclusion, U.S. Pat. No. 4,375,954 A discloses a burner fueled with a combination of gas and oil. This burner features a ring-shaped preheat chamber in which the oil is first heated by means of a combustion gas, after which the heated oil is jetted by a central nozzle into the combustion chamber for combustion. But, the burner involved in this case is not devised for surface coating substrates, it being simply a conventional burner.